Our planet is full of some truly amazing natural phenomena. It’s really incredible the kinds of things that nature can do entirely on its own – sometimes, you’d swear it was a trick.

One such phenomenon is the “cross sea,” most famously observed near a small island off the western coast of France. The Isle of Rhé is home to gorgeous beaches and sunny weather, which attracts tourists from all over Europe. But we’re not here to talk about sunny summer vacations, we’re here to discuss one of the weirdest naturally-occurring phenomena you could ever hope to witness.

Photo Credit: Youtube

A cross sea honestly looks beautiful from afar, with its strangely perfect geometric pattern of waves – but it’s actually very dangerous! This grid pattern occurs when two wave systems cross each other while traveling at slanting angles. The resulting waves turn the ocean into a perilously swirling place for swimmers and boats.

Photo Credit: Wikimedia Commons

Cross seas have been known to sometimes produce really tall waves and have caused their fair share of ship accidents.

Photo Credit: NOAA

Cross seas don’t just occur by the Isle of Rhé – they can occur in coastal places around the globe. So if you ever happen to see one, take a photo, but stay out of the water!